Our long-term objective is to further develop and evaluate the effectiveness of a comprehensive early and preventive intervention program for young children (ages 4-6) who have already been given a previous diagnosis of Attention Deficit Hyperactivity Disorder (ADHD). Our specific aims are to further develop intervention procedures that can reduce risk factors that may; (a) exacerbate or maintain initial problem behaviors, (b) contribute to the development of later comorbid conditions and/or that may be common underlying risk factors for other disorders (e.g., conduct disorder), and (c) necessitate the need for or continued use of stimulant medication. In addition to those components known to contribute to effective early intervention, the Summer Treatment and Research (Star) program includes the following features that are innovative to early intervention programs for ADHD; (a) an intensive classroom-based summer program that emphasizes comprehensive assessment across domains, (b) the use of (experimental) functional analysis to develop the most effective behavioral treatments, (c) comprehensive medication evaluations that simultaneously assess the relative and combined effects of medication at varying dosages and behavioral treatments at varying levels of treatment strength, and (d) a unique combination of a social and sports skills training program. We aim to conduct preliminary longitudinal evaluations (i.e., two years) of the effectiveness of the overall program using (a) an intensive study of the individual case, (b) ongoing, multi-method outcome measures collected at least weekly and monthly, (c) repeated annual psychometric evaluations, and (d) repeated annual psychiatric evaluations.